372 builders, port numbers any idea's how she will be?

[lostone]

https://classifieds.ksl.com/listing/57303969

I have been watching this one for a bit. Like I said if he would come down on price then I would consider it. Where I am wanting a lathe for rifle barrels also I am thinking I would be better off though to hold out for a https://www.precisionmatthews.com/s...MIuYaclNiX5wIVDr7ACh1QbQESEAAYASAAEgLYlPD_BwE and kill two birds with one stone. Nothing wrong with the older lathe and if I was only after doing cylinders then it would be perfect. If you can't tell I'm trying to talk myself out of offering this guy 2K for his LOL.

 

[Yotaismygame]

If you’re thinking of going with a Chinese brand I’d go with grizzly. Seems to be the brand everyone recommends. Pretty sure all the Chinese lathes come from the same place. But what I’ve read is grizzly does their own work to them before they go up for sale.

 

[Yotaismygame]

$2500 seems steep. Picked up my Logan for $1200.

and here’s a clausing for cheap.

 

[lostone]

The Precision Matthew is made in Taiwan and I think the Grizzly gunsmith versions are also. From what I have read the Precision has a higher quality bearing set and better chucks is the reason I have been looking at them. For the price of the one you listed I would own it if it was close to me and the ways where in good shape.

 

[Yotaismygame]

I like my Logan which is only a 10x24. Perfect size for my needs and space available. I enjoy using a classic American made machine. But! New parts are super expensive and finding used isn’t always available. I do partially wish I would have bought a new similar sized lathe.

 

[trappermike]

I have a couple of machinist buddies,they both bought Advance brand lathes made in Taiwan,quality was excellent.

 

[lostone]

I have a couple of machinist buddies,they both bought Advance brand lathes made in Taiwan,quality was excellent.

That is what I have been hearing on a machinist forum that I follow as well.

Any of the newer equipment that is made anywhere besides China or Taiwan is out of my reach as a hobbyist, after reading about it a lot it seems you can buy Chinese and then pay a lot to get it into decent shape or just buy Taiwan to begin with and have it running proper. I also like the older equipment but a lot of it has so much time on it that it's showing it's age and the cost to bring it back to spec is prohibitive, or at least as far as lathes go. When it comes time to get myself a milling machine I will be considering older equipment but I will take my time until I can find what is in decent shape for a reasonable price.

 

[trappermike]

Well I hate lowering cylinders to gain a little less squish clearance,that reduces transfer and ex. duration which I think is much more important. I never fret over blowdown figures because I'm gonna raise the stock ex. port and increase that number anyway. Your 372 has great transfer ports to start with so I wouldn't butcher them.More ex. dur. gives more power,yes compression drops slightly as you raise it,but for more hp it wins. In smaller motors like yours I would not make in. dur. too long or low speed power will really suffer.
Now everyone has their own thoughts on port timing so I'm expecting lotsa flak.
I only really fret over squish clearance when I''ve raised the ex. to where I want it and comp. drops below what I'd like,then I'll squeeze squish gap to minimum to regain comp. Ex. port timing makes way more HP than compression.
Put 220 lbs. comp. in a 2-stroke lawn mower engine,the compare it to a race motor with 140 lbs. comp.,no contest,port timing is what all high output motors use... The key is not to lose low speed power for your application.
On the other hand if I had a small 2-stroke and it needed more low and mid power,more comp. will definitely work.

 

[trappermike]

Me and a whole pile of guys had to move his new Advance lathe from my truck into his basement,wow the thing was heavy,but all the weight was on the gearbox end making it far harder,not a job I'd wanna do again.

 

[Yotaismygame]

Well I hate lowering cylinders to gain a little less squish clearance,that reduces transfer and ex. duration which I think is much more important. I never fret over blowdown figures because I'm gonna raise the stock ex. port and increase that number anyway. Your 372 has great transfer ports to start with so I wouldn't butcher them.More ex. dur. gives more power,yes compression drops slightly as you raise it,but for more hp it wins. In smaller motors like yours I would not make in. dur. too long or low speed power will really suffer.
Now everyone has their own thoughts on port timing so I'm expecting lotsa flak.
I only really fret over squish clearance when I''ve raised the ex. to where I want it and comp. drops below what I'd like,then I'll squeeze squish gap to minimum to regain comp. Ex. port timing makes way more HP than compression.
Put 220 lbs. comp. in a 2-stroke lawn mower engine,the compare it to a race motor with 140 lbs. comp.,no contest,port timing is what all high output motors use... The key is not to lose low speed power for your application.
On the other hand if I had a small 2-stroke and it needed more low and mid power,more comp. will definitely work.

That's really interesting mike. Sounds like we port almost completely different ways. I'm going to have to port a saw like how you described to see it for myself. There's not many porters on here and that ones that are seem to be chill most of the time. I try to keep and encourage and open mind around here when it comes to porting. I'm still learning, we all still learning.

 

[trappermike]

Well I've been studying and building 2-stroke sine 1972,I have a huge database on all race and stock engines ,motorcycles,kart engines,snowmobiles,since then,I call it my "archives",it's all on paper(a massive file) since I don't trust losing data on computers,because I'm stubbornly old fashioned.
To get more ultimate horsepower from a 2-stroke you gotta raise the ex. port,you will lose some low speed power as you do.Max. ex. timings I use are pretty damn high,not for work saws of course,but the numbers may surprise you,which unfortunately I won;t reveal.
But more hp in 2-strokes mean more ex. duration,then try to balance the other ports to work with it,comp. etc.,and carb size (very vital),and of course a pipe if you wanna go that far.

 

[trappermike]

I would much rather raise a cyl.1mm creating a bigger squish gap,but gain a good boost in port timing in trans. and ex.which will make more power.You have to jiggle all these figures to try to get what you want.
In bigger motors like 100cc,125,c or 140 cc,you don;t so much worry of loss of low speed power, For them you dont worry of loss of low speed power,push the numbers to the max,if carb size and pipe are correct you;ll have a brutally poweful saw.

 

[lostone]

With EX timing Mike are you thinking the additional compression hurts on the up stroke or are you thinking that the additional EX time is clearing the chamber for more intake and creating the power there. Keep in mind I don't know much about this and it's interesting to see what the reasons are for doing things.

 

[huskihl]

For a work saw, I’ll take torque every time. It won’t win races, but it doesn’t kill the saw when your dog in. The height of my exhaust and transfers depends on what the owner wants to do with it. The only thing I have ever built with more than 170° of exhaustion duration was a race saw. Drop that in to a 24 inch Sugar Maple and it would fall on its face unless it was above 70cc

 

[Yotaismygame]

@lostone Wish I had this bad boy in my garage

 

[lostone]

I would be happy with.
https://classifieds.ksl.com/listing/57844680

 

[Yotaismygame]

Looks like a pretty late model Logan.

 

[Ketchup]

Watch for EMCO (not ENCO) lathes. They are super high quality and most people don’t know what they are. As good as Clausing IMO.
My Logan 810 is exactly like what @Yotaismygame descibed. Fits in my shop, does the job, but isn’t amazing. Still wonder if I should have bought a lathe new.

For a work saw, I’ll take torque every time. It won’t win races, but it doesn’t kill the saw when your dog in. The height of my exhaust and transfers depends on what the owner wants to do with it. The only thing I have ever built with more than 170° of exhaustion duration was a race saw. Drop that in to a 24 inch Sugar Maple and it would fall on its face unless it was above 70cc

This is much more in keeping with my own experience. Little saws don’t seem to like low compression or high exhaust duration. The high exhaust/lowish comp strategies are very interesting though. My 372 is in pieces again. I might try stacking some gaskets on a 372 and see what I can make for RPM.

@trappermike, your insights are extremely interesting. Please keep sharing.

 

[huskihl]

Watch for EMCO (not ENCO) lathes. They are super high quality and most people don’t know what they are. As good as Clausing IMO.
My Logan 810 is exactly like what @Yotaismygame descibed. Fits in my shop, does the job, but isn’t amazing. Still wonder if I should have bought a lathe new.



This is much more in keeping with my own experience. Little saws don’t seem to like low compression or high exhaust duration. The high exhaust/lowish comp strategies are very interesting though. My 372 is in pieces again. I might try stacking some gaskets on a 372 and see what I can make for RPM.

@trappermike, your insights are extremely interesting. Please keep sharing.

Never heard much about racing fuel for 5:1 cr engines. Prolly could get away with 82 octane

 

[Yotaismygame]

Watch for EMCO (not ENCO) lathes. They are super high quality and most people don’t know what they are. As good as Clausing IMO.
My Logan 810 is exactly like what @Yotaismygame descibed. Fits in my shop, does the job, but isn’t amazing. Still wonder if I should have bought a lathe new.

This is much more in keeping with my own experience. Little saws don’t seem to like low compression or high exhaust duration. The high exhaust/lowish comp strategies are very interesting though. My 372 is in pieces again. I might try stacking some gaskets on a 372 and see what I can make for RPM.

@trappermike, your insights are extremely interesting. Please keep sharing.

One of the 268 pop up piston saws I did for myself had an exhaust at 97 but only made 160psi. She ran real strong. Intake was at 86 I think and the blow down was around 25-28. I didn’t move the transfers so it must of had a long blow down.

pretty opposite of how I build a 372 now.